This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Gigabit Ethernet (GigE) has rapidly gained prominence and acceptance as the new step in evolution of networks. Relatively low-cost, high-speed, and interoperable with today's de facto standard, 100 Mbps Fast Ethernet, are just a few of GigE's promises. For many network planners, it is really only a matter of time before they adopt GigE.
Although Gigabit Ethernet is interoperable with 10/100 Mbps, there are some important differences that bear careful consideration. One of the most important is the absence of any standard Maximum Transmission Unit or MTU. The 1500 bytes standard MTU of 10 and 100 Mbps networks has been replaced with no standard at all. Packets on Gigabit Ethernet can be any size supported by network vendors, varying from 1500 bytes to over 16000 bytes. Vendors are constrained by the component manufacturers who typically limit largest supported frame size to around 9000 bytes.
While the benefits of so-called jumbo packets are significant: jumbo packets can more than double accessible bandwidth on today's networks compared to using smaller 1500 bytes packets, there are some hidden perils. Due to the lack of standard MTU values, MTU conflicts may hamper 100-Mbps-to-Gigabit transitions. For example, various forms of MTU conflict, such as black holes, can devastate network performance.
By sending oversize packets to an end-host and receiving messages back from intermediate interfaces, a transmitting host can discover the path MTU to a specific end-host, and adjust its traffic patterns accordingly. If not properly configured, or if messages are indiscriminately blocked on Layer 3 interfaces, necessary messages will not find their way to a source interface. These devices are referred to as black holes.
The term “jumbo” has typically been applied to any network unit (frame, packet, MTU) that is greater than the 10/100 Mbps Ethernet standard: at Layer 3 (packets and MTU), the standard size is 1500 bytes. Jumbo packets are one of the obvious differences between 100 Mbps and GigE. However, there is also a looming issue in that Gigabit Ethernet standard has no default Maximum Transmission Unit (MTU). MTU is a Layer 3 parameter that controls the maximum packet size allowed on the network. For 10 and 100 Mbps Ethernet, the standards (RFC 894, 895) clearly set the largest MTU to 1500 bytes and almost all Ethernet interface cards defaulted to it.
But, in current implementations, GigE data transfer performance is strongly dependent on MTU: recent studies have shown that jumbo packets permit most hosts to send data at much higher transfer rates than the smaller 1500 byte packets. In this context, there is a need to multiplex jumbo packets generated by different sources into RTP packets.
In the state of the art, it is well known to compact multi-packets into a single RTP packet, in order to reduce header overhead or to wrap multiple user data into a single RTP packet, in order to transfer multi-user data within a single RTP session. But, these existing RTP multiplexing methods are all based on standard packet RTP applications. They can't be used when different types of data, like video data, audio data, or metadata are transferred in Ethernet Jumbo packets.
Recent application, like for example, HiPerNet cameras can generate various output streams comprising data of different types, such as: DPX wrapped video, AIFF audio signal which maintains time relation with the video content, Intercom audio also presented as AIFF audio, where there is no time relation with the video content and at least, metadata. All these output streams are generated as Ethernet IP-UDP-RTP jumbo packets.
One of the goals of the present invention is to transmit simultaneously these data belonging to different types generated as Ethernet IP-UDP-RTP jumbo packets on a high-speed IP network.
Certain aspects commensurate in scope with the disclosed embodiments are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.